Colorectal cancer is one of the leading causes of death in North America, with the number of new cases of this disease ranked second only to the number of new cases of lung cancer [American Cancer Society, Vol 38, Jan. and Feb. (1988), p.15]. In spite of its prevalence among humans, spontaneous adenocarcinoma of the colon appears to be quite rare in other mammalian species, including primates. A notable exception is the high incidence of spontaneous colonic carcinomas in the cotton-top tamarin, Saquinus oedious oedipus.
The malignancy was first identified in tamarins housed at the Oak Ridge Associated Universities (ORAU) Marmoset Colony in the late 1960's [Lushbaugh et al., Prim. Med; Vol. 10, pp. 119-134 (Karger, Basel 1978)]. Subsequently, in excess of 190 cases of colorectal adenooaroinoma have been diagnosed in 11 separate animal facilities housing colonies of S. oedious primates (Clapp, 1988, unpublished informal survey). Detailed descriptions of the colon pathology and histological characteristics of the tamarin colon cancer have been presented (Lushbaugh, et al, Ibid., 1978; Swartzendruber and Richter, Lab. Invest., Vol. 43, No. 6, 1980, pp. 523-529; Lushbaugh, et al.; Dig. Dis. and Sci., New Series Vol. 30 No. 12, Dec. 1985, pp. 119S-125S; and, Clapp, et al., Ibid., 1985). Briefly, the cancer appears to arise at the base of colonic crypts, and progresses into poorly-defined colonies which may displace other cells for the full thickness of the mucosa, prior to forming a malignant ulcer. The cancer is multicentric in origin, and metastasizes to mesenteric lymphatic channels and nodes quite commonly. Histologically, the carcinoma is poorly differentiated, comprising highly mitotic stem-cells, mucin-producing cells, argentaffin cells and absorbtive cells in various stages of differentiation. Cells are easily stained with the PAS stain, which demonstrates that some of the malignant cells always produce mucin. In the animal, PAS positive neoplastic cells are detectible in primary sites, lymphatics and secondary sites. These cells exhibit fine granularity of the cytoplasm, intracytoplasmic cysts with positive mucin content, and typical goblet or signet ring mucin-secreting cells.
Adenocarcinoma of the colon in tamarins resembles the human disease in "unknown etiology, epithelial cell types involved, apparent relationship to chronic colitis, local invasiveness, and propensity for easily metastatic spread", as discussed by Lushbaugh et al. (Comp. Pathol. Bull. Vol. 15, pp. 2-4, 1983). Indeed, the spontaneous appearance of colorectal adenocarcinoma in the cotton-top tamarin has been proposed as an animal model for the human disease (Lushbaugh et al., Ibid., 1983; Clapp et al., in Carcinoma of the large Bowel and Its Precursors, pp. 247-261, Alan r. Liss, Inc., 1985). Because of the uniqueness of this primate cancer, considerable efforts have been made by several laboratories to establish continuous cell-lines from tumor material of affected animals. Although methodology has been described for the initiation of cell-lines from colorectal adenocarcinomas from several species, including rats (Borman et al., Cancer Res., Vol. 42, pp. 6074-6083, Dec. 1982); mice (Tan et al., J. Nat. Cancer Inst., Vol. 56 No. 4, pp. 871-873, Apr. 1976); guinea pigs (O'Donnell and Cockerell, Cancer Res. Vol. 41, pp. 2372-2377, June 1981), and human tumors (Tomkins et al., J. Nat Cancer Inst., Vol. 52 No. 4, Apr. 1974; Willson et al., Cancer Res., Vol. 47, pp. 2704-2713, May 15, 1987; Whitehead et al., Cancer Res., Vol. 47, pp. 2683-2689, May 15, 1987), earlier attempts to culture biopsies of the tamarin colorectal tumor have uniformly met with failure.